Thermal reactor for internal combustion engine fuel management system

ABSTRACT

A fuel management system for an internal combustion engine including an intake manifold is presented. The fuel management system includes a thermal reactor having an inlet port and an outlet port. The thermal reactor receives liquid fuel through the inlet port and is adapted to heat the liquid fuel and discharge fuel vapor through the outlet port. A pressure sensing device is configured to measure pressure within the intake manifold to determine engine load. A plenum is adapted to receive the fuel vapor from the outlet port and mix the fuel vapor with air, and the plenum is adapted to be connected to the intake manifold to provide the fuel vapor and air mixture to the intake manifold. A fuel metering device is operable to regulate the amount of fuel vapor provided to the plenum in response to the pressure sensing device.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a division of U.S. patent application Ser.No. 09/176,011, now U.S. Pat. No. 6,330,825, which claims the benefit ofU.S. Provisional Patent Application No. 60/063,183, filed Oct. 20, 1997.The entire disclosures of the referenced applications are incorporatedby reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to internal combustion engines, and moreparticularly, to a fuel management system for an internal combustionengine fueled by a liquid hydrocarbon.

[0004] 2. Description of Related Art

[0005] The operation of internal combustion engines is well known. In aninternal combustion engine, combustion of fuel takes place in a confinedspace, producing expanding gases that are used to provide mechanicalpower. The most common internal-combustion engine is the four-strokereciprocating engine used in automobiles. Here, mechanical power issupplied by a piston fitting inside a cylinder. On a downstroke of thepiston, the first stroke, fuel that has been mixed with air (by fuelinjection or using a carburetor) enters the cylinder through an intakevalve via an intake manifold. The intake manifold is a system ofpassages that conduct the fuel mixture to the intake valves. The pistonmoves up to compress the mixture at the second stroke. At ignition, thethird stroke, a spark from a spark plug ignites the mixture, forcing thepiston down. In the exhaust stroke, an exhaust valve opens to vent theburned gas as the piston moves up. A rod connects the piston to acrankshaft. The reciprocating (up and down) movements of the pistonrotate the crankshaft, which is connected by gearing to the drive wheelsof the automobile.

[0006] A diesel engine is another type of internal-combustion engine. Itis generally heavier and more powerful than the gasoline engine andburns diesel fuel instead of gasoline. It differs from the gasolineengine in that, among other things, the ignition of fuel is caused bycompression of air in its cylinders instead of by a spark. The speed andpower of the diesel are controlled by varying the amount of fuelinjected into the cylinder.

[0007] In this disclosure, a fuel is defined as a substance that can beburned by supplying air and a sufficient amount of heat to initiatecombustion. A liquid hydrocarbon fuel, such as gasoline or diesel fuel,must be converted to a gas before it can be ignited. This liquid to gasvapor conversion is required because the molecules of fuel must be wellmixed with the molecules of air before they can chemically react witheach other to give off heat.

[0008] However, not all of the liquid fuel must be converted to a gasbefore combustion can occur. Just enough fuel needs to be converted to agas so that the mixture of gas molecules and air molecules falls withinthe fuel's flammability limits—which refers to the minimum and maximumconcentration percentages, by weight, of fuel in air that will burn. Ifthe concentration of the gaseous fuel in air is less than the minimum orgreater than the maximum flammability limit, the fuel and air mixturewill not ignite. Known internal combustion engines and fuel deliverysystems are inefficient in converting the liquid fuel to a gaseousstate. Therefore, the fuel and air molecules cannot mix properly forcomplete combustion.

[0009] In a gasoline engine employing a standard automotive throttlebody fuel injection system, this inefficiency is due at least in part tothe high velocity of the air and fuel s mixture passing the fuelinjection's throttle body, which may reduce the inlet temperature as lowas 40° F. (4° C.). The flash point temperature—the temperature at whichthe fuel will give off enough vapor to form a combustible mixture withair—for gasoline is 45° F. (7° C.). This reduction in inlet temperaturereduces the amount of heat available from the atmosphere to evaporatethe fuel. Since less ambient heat is available, more energy fromcompressing the mixture is required to evaporate the fuel.

[0010] Gasoline engines have a throttle valve to control the volume ofintake air. The amount of fuel and air that goes into the combustionchamber regulates the engine speed and, therefore, engine power. Thiscauses continuous changes in the atmospheric air velocity due to thepressure differential between the atmosphere and the intake manifold.These pressure variations cause the size of the particles of atomizedfuel to vary throughout the engine's RPM range. As a result, there is awide variation in fuel droplet size in the air stream. Therefore, thefuel droplets have less surface area exposed to the air for evaporationand more heat is required to fully evaporate the fuel.

[0011] Once the fuel vapor and air mixture leaves the throttle bodyinjector and enters the intake manifold, the mixture velocity is so highthat some of the fuel droplets are centrifuged out of the air streamwhen they make turns. This occurs because the fuel droplets are heavierthan air. This varies that portion of the mixture's stoichiometric fuelto air ratio, even though the overall air to fuel ratio of the mixtureflowing through the fuel injector is correct. The portion of the mixturethat contains the fuel that was centrifuged out of the main air streamreduces the amount of surface area exposed by the fuel to the air forevaporation. This increases the amount of energy required to evaporateit. Once this portion of the fuel mixture is evaporated, it burns richsince the original portion of this mixture was rich from the fuel beingcentrifuged out of the main air stream. Carbony residues that accumulatein the combustion chambers and darker areas on the piston tops indicateareas of excessive fuel richness during combustion.

[0012] Conversely, portions of the air stream that are lean, but stillfall within the flammability limits, will burn and cause extremely hightemperatures. Auto-ignition temperature refers to the temperature atwhich a mixture of air and fuel will spontaneously ignite without openflame, spark, or a hot spot. The auto-ignition temperature of gasolineis 495° F. (275° C.). When these localized high temperature areas reachhigh enough pressure and temperature, autoignition of the end gases willresult, causing detonation, which is the uncontrolled combustion orexplosion caused by auto-ignition of the end gases that were notconsumed in the normal flame front reaction. Detonation results in thefamiliar “ping” or “spark knock” sound.

[0013] The engine's heat of compression during the compression strokeproduces heat that begins to evaporate the air and fuel mixture in thecylinder. However, this compressing of the mixture increases thepressure. As a result, the increased pressure increases the boilingpoint of the fuel for evaporation. Evaporation continues slowly becausethese relationships are not linear. So enough fuel evaporates, allowingit to fall within its flammability limits. Then the spark plug ignitesthe mixture and creates a flame front. This flame front during thecombustion process has the same effect of increasing the boiling pointof the fuel so its critical temperature is never reached. Therefore, theremaining atomized fuel droplets do not evaporate before or duringcombustion. Since the droplets are not vaporized, they do not bum.

[0014] When the cylinder pressure falls due to the descent of the pistonwhile on the power stroke, the fuel droplets that were not evaporatedearlier now evaporate due to a lower boiling point and higher cylindertemperature. These evaporated fuel droplets now burn, but they bum toolate into the crankshaft angle for producing power. Thus, less power andhigh exhaust gas temperatures result.

[0015] Direct (intake) port fuel injection has better fuel distributioncharacteristics than a throttle body fuel injection system. However,they allow very little time to evaporate fuel in the intake port.Therefore, the heat of compression must heat the air/fuel mixture forevaporation before combustion can occur. This system has the sameinherent inefficiencies regarding the engine's heat of compression,which increases the boiling point of the fuel. Therefore, as thecylinder pressure rises, the critical temperature is never reached. Theremaining fuel droplets do not burn in time to produce power. Thus, lesspower and high exhaust gas temperatures still result.

[0016] The heat of combustion (the temperature in the cylinder due tocombustion) for gasoline is 840° F. (449° C.) plus or minus 40° F. (4°C.) above ambient. Conventional automotive exhaust gas temperatures are1,400 to 1,500° F. (760 to 815° C.). This temperature difference (heatenergy) between the exhaust gas temperature and the heat of combustionis totally wasted as excessive exhaust gas temperature. Even theengine's cooling system must be enlarged to dissipate the higher exhaustgas temperatures due to the increased temperature differential aroundthe exhaust side of the combustion chambers and exhaust ports. Thiswasted heat energy is dissipated to the atmosphere through the vehicle'sradiator, and an equal amount of wasted heat energy is dissipatedthrough the vehicle's exhaust pipes as excessively high exhaust gastemperatures.

[0017] The remaining fuel that did not chemically react in thecombustion chamber or in the exhaust manifold then enters a 2,000° F.(1,093° C.) catalytic converter for combustion. The unburned fuel thatescapes the catalytic converter enters the atmosphere as hydrocarbon andcarbon-monoxide pollutants. Moreover, currently produced catalyticconverters are only effective when the engine is at operatingtemperature, so it has no effect on cold start emission levels.

[0018] Similar shortcomings exist with known diesel engines. In dieselengines with indirect fuel injection (precombustion chamber), theengine's heat of compression during the compression stroke produces heatthat begins to evaporate the air and fuel mixture in the cylinder.However, this compressing of the mixture increases the pressure. As aresult, the increased pressure increases the boiling point of the fuelfor evaporation. Evaporation continues slowly because theserelationships are not linear, and just enough of the aromatics in thediesel fuel evaporate allowing it to fall within its flammabilitylimits. The flash point temperature of the aromatics is low enough forthe air and fuel mixture to auto-ignite, which results in a flame front.This flame front ignites more of the fuel mixture during the combustionprocess; however, it has the same effect of increasing the boiling pointof the fuel so its critical temperature is never reached. Therefore, theremaining liquid fuel droplets do not evaporate before or duringcombustion.

[0019] Diesel engines with direct-injection (DI) have even greater fuelvaporization problems. In a diesel engine with DI high turbulencecombustion chambers, the fuel spray pattern elongates in response to airflow. The smaller fuel droplets concentrate on the leading (lower) edgeof the spray pattern while the larger and heavier droplets remainclustered about the core.

[0020] Ignition begins as a series of small bursts at the interfacebetween the fuel spray and cylinder air, where there is surplus ofoxygen. The bursts combine into flame fronts that progressively moveinto the fuel-soaked core of the pattern. Every normal combustion eventin a diesel engine begins under oxygen-rich conditions and concludesunder oxygen-lean conditions. This variability in fuel/air ratios is aspecial burden of the diesel engine. In addition, diesel engines operateunder a fairly wide range of loads and speeds. Air turbulence, durationof the expansion stroke (power), and cylinder temperature vary with theoperating mode.

[0021] Hydrocarbons survive their passage through the cylinder when themixture is either too lean or too rich to burn. Excessively leanmixtures are caused by fuel droplets that break free of spray plume anddiffuse throughout the combustion chamber. The resulting fuel mixturedoes not support combustion, and the raw fuel exists through theexhaust. This phenomenon often occurs under light loads and at lowengine speeds, which causes high hydrocarbon emission spikes duringidle. Hydrocarbon emissions are also generated when the flame isquenched by too rapid infusion of air or by contact with the relativelycool cylinder walls.

[0022] Particulate Matter (PM) in high concentrations that accompanydiesel acceleration and cold starts can be seen as black smoke. Thehydrocarbon component of PM, referred to as soluble organic fraction(SOF), consists of combustion by-products, lube oil and unburned fuel.Soot, the SOF carrier, forms in the oxygen-poor (rich fuel mixture)region on the trailing edge of the fuel plume. Oxides of nitrogen (NOx)are created in the high-temperature, oxygen-rich combustion (fuel-leanmixture) that occurs on the leading edge of the spray plume. Most sootforms early in the combustion process when fuel accumulates during theignition lag period, then burns at extremely high temperatures to formNOx.

[0023] When the cylinder pressure falls due to the descent of the pistonwhile on the power stroke, the fuel droplets that were not evaporatedearlier now evaporate due to a lower boiling point and higher cylindertemperature. These evaporated fuel droplets now burn, but they bum toolate into the crankshaft angle for producing power. Thus, less power,high emission levels, and high exhaust gas temperatures result.

[0024] The heat of combustion for diesel fuel is 500 to 550° F. (260 to288° C.) above ambient. Convention diesel exhaust gas temperatures are1,100 to 1,300° F. (593 to 704° C.). As with a gasoline engine, thistemperature difference (heat energy) between the diesel exhaust gastemperature and the heat of combustion is totally wasted as excessiveexhaust gas temperature. Thus, the engine's cooling system must beenlarged to dissipate the higher exhaust gas temperatures due to theincreased temperature differential around the exhaust side of thecombustion chambers and exhaust ports. This wasted heat energy isdissipated to the atmosphere through the vehicle's radiator, and anequal amount of wasted heat energy is dissipated through the vehicle'sexhaust pipes as excessively high exhaust gas temperatures.

[0025] The present invention addresses some of the above mentioned, andother, shortcomings associated with the prior art.

SUMMARY OF THE INVENTION

[0026] In one aspect of the present invention, a fuel management systemfor an internal combustion engine is presented. The internal combustionengine includes, among other things, an intake manifold, and the fuelmanagement system includes a thermal reactor having an inlet port and anoutlet port. The thermal reactor receives liquid fuel through the inletport, and is adapted to heat the liquid fuel and discharge fuel vaporthrough the outlet port. A pressure sensing device is configured tomeasure pressure within the intake manifold to determine engine load,and a plenum is adapted to receive the fuel vapor from the outlet portand mix the fuel vapor with air. The plenum is adapted to be connectedto the intake manifold to provide the fuel vapor and air mixture to theintake manifold. A fuel metering device is operable to regulate theamount of fuel vapor provided to the plenum in response to the pressuresensing device.

[0027] In another aspect of the invention, a thermal reactor forconverting a liquid hydrocarbon fuel to a fuel vapor includes a cylinderdefining an axial bore therethrough. The cylinder further defines aninlet port adapted to receive the liquid hydrocarbon fuel, and an outletport adapted to discharge the fuel vapor. At least one heating elementis connected to the cylinder and is arranged to heat the liquidhydrocarbon fuel to convert the liquid fuel to the fuel vapor.

[0028] In yet another aspect of the present invention, a system forpreventing cylinder over scavenging during the overlap period of acamshaft in an internal combustion engine is provided. The engineincludes an exhaust manifold and an exhaust pipe coupled thereto. Thesystem includes a pressure sensor to measure back pressure of exhaustgas from the engine and a control valve coupled to the exhaust pipe. Thecontrol valve is responsive to the pressure sensor to restrict theexhaust gases and apply back pressure on the engine.

[0029] In a still further aspect, a method of dynamically mappingoperating parameters of an engine is provided. The method includesconfiguring a plurality of measurement devices to indicate a pluralityof engine parameters, operating the engine, recording the outputs of themeasurement devices while the engine is operating, and playing back therecorded outputs at predetermined time intervals. In a particularembodiment, the recording of the outputs comprises video taping theoutputs of the measurement devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other objects and advantages of the invention will becomeapparent upon reading the following detailed description and uponreference to the drawings in which:

[0031]FIG. 1 is a block diagram illustrating a fuel management system inaccordance with an embodiment of the present invention;

[0032]FIG. 2 is a block diagram illustrating a fuel management system inaccordance with an alternative embodiment of the present invention;

[0033]FIG. 3 is a block diagram illustrating a fuel management system inaccordance with another alternative embodiment of the present invention;

[0034]FIG. 4 is a side view of an embodiment of a thermal reactor inaccordance with the present invention;

[0035]FIG. 5 is a front perspective view of a cylinder suitable for athermal reactor such as the embodiment illustrated in FIG. 4;

[0036]FIG. 6 is a perspective view of a first end plate for a thermalreactor such as the embodiment illustrated in FIG. 4;

[0037]FIG. 7 is a perspective view of a second end plate for a thermalreactor such as the embodiment illustrated in FIG. 4;

[0038]FIG. 8 is a perspective view of a cylinder adapted for analternative embodiment of a thermal reactor in accordance with thepresent invention;

[0039]FIG. 9 is a front perspective view of a fuel metering device inaccordance with an embodiment of the present invention;

[0040]FIG. 10 is a top perspective view of the fuel metering deviceshown in FIG. 9;

[0041]FIG. 11 is a side perspective view of the fuel metering deviceshown in FIG. 9;

[0042]FIG. 12 is a block diagram illustrating a fuel management systemin accordance with yet another alternative embodiment of the presentinvention;

[0043]FIG. 13 is a perspective view of a plenum in accordance with anembodiment of the present invention;

[0044]FIG. 14 is a block diagram illustrating an exhaust control systemin accordance with an embodiment of the present invention;

[0045]FIG. 15 is a perspective view of an exhaust system thermal reactorin accordance with the present invention; and

[0046]FIG. 16 illustrates a glow plug system in accordance with anembodiment of the present invention;

[0047]FIG. 17 is a flow diagram illustrating a mapping process inaccordance with an embodiment of the present invention.

[0048] While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0049] Illustrative embodiments of the invention are described below. Inthe interest of clarity, not all features of an actual implementationare described in this specification. It will of course be appreciatedthat in the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers'specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

[0050]FIG. 1 is a block diagram illustrating a fuel management system100 in accordance with one embodiment of the present invention. Specificembodiments of the present invention are configured for use as an add-onsystem for an original equipment manufacture's (OEM) engine. The fuelmanagement system 100 is adapted for use with an internal combustionengine 110 using a liquid hydrocarbon fuel 112, such as gasoline, dieselfuel, kerosene, alcohols, etc., which is typically contained in a fueltank. Among other things, the engine 112 includes an intake manifold 114for conducting an air/fuel mixture to the intake valves (not shown) ofthe engine 112.

[0051] The exemplary fuel management system 100 includes a thermalreactor 120 having an inlet port 122 and an outlet port 124. The thermalreactor 120 receives liquid fuel 112, typically from a vehicle's fueltank, through the inlet port 122. The thermal reactor 120 heats theliquid fuel 112 to convert it to fuel vapor, which is then dischargedthrough the outlet port 124. A plenum 126 receives the fuel vapor andthoroughly mixes it with air. The fuel vapor and air mixture then flowsfrom the plenum 126 to the intake manifold 114 to provide the fuel vaporand air mixture to the intake manifold. A pressure sensing device 128 isconfigured to measure pressure within the intake manifold 114 todetermine engine load, and a fuel metering device 130 is operable toregulate the amount of fuel vapor provided to the plenum 126 in responseto the pressure sensing device 128, thus providing the leanest possibleair to fuel vapor ratio for the engine 112 load condition. In certainembodiments adapted for use with a turbocharged engine, such as aturbocharged diesel engine, the engine's native turbocharger may providethe function of the plenum 126. Hence, the plenum 126 would not benecessary in such an implementation, and the fuel vapor from the thermalreactor 120 would be provided directly to the turbocharger.

[0052] The fuel metering device 130 may be situated in various positionsrelative to the thermal reactor 120 in accordance with variousembodiments of the invention. In a particular embodiment, such as thesystem 101 illustrated in FIG. 2, the fuel metering device 130 isconnected to the outlet port 124 of the thermal reactor 120, such thatthe fuel vapor passes from the thermal reactor 120 outlet port 124,through the fuel metering device 130, to the plenum 126. In anotheralternative embodiment shown in FIG. 3, the fuel metering device iscoupled to the inlet port 122 of the thermal reactor 120, such that theliquid fuel 112 passes through the fuel metering device 130 to thethermal reactor inlet 122.

[0053] Turning now to FIG. 4 and FIG. 5, an exemplary thermal reactor120 in accordance with a particular embodiment of the invention isillustrated. The thermal reactor 120 functions to heat liquid fuel toconvert it to a fuel vapor, and further, it serves as a surge tank offuel vapor to meet engine demands while liquid fuel is being processed.The thermal reactor 120 comprises a cylinder 140 defining an axial bore142 therethrough. The cylinder 140 is adapted to receive the liquid fuel112 from the inlet port 122 and discharge the fuel vapor through theoutlet port 124. In the particular embodiment illustrated in FIG. 4 andFIG. 5, a first end plate 144 that is connected to a first end 145 ofthe cylinder 140 defines the inlet port 122, and a side wall 146 of thecylinder 140 defines the outlet port 124. At least one heating element148 is provided to heat the liquid fuel and thus, to convert the liquidfuel to the fuel vapor.

[0054] The thermal reactor 120 shown in FIG. 4 and FIG. 5 includes aplurality of heating elements 148 disposed in the cylinder 140, with theheating elements 148 arranged such that the liquid fluid contacts theheating elements 148. The side wall 146 of the cylinder 140 has aplurality of apertures 150 extending therethrough, with each of theapertures 150 having one of the heating elements 148 extendingtherethrough, so that each heating element 148 projects into thecylinder 140 (only two heating elements 148 are shown extending throughthe apertures 150 in FIG. 5 to simplify the illustration). In certainembodiments, each of the heating elements 148 is positioned generallyperpendicular to the axis of the cylinder 140, and each of the apertures150 has a corresponding aperture 150 located about 90 degrees therefrom,as illustrated in FIG. 5. More specifically, the apertures 150 arearranged in two columns, with each column being generally parallel tothe axis of the cylinder 140 and positioned about 90 degrees apart.

[0055] In one specific embodiment of the thermal reactor 120A, thecylinder 140 is about 12.125 inches (30.80 cm) long, with a diameter ofabout 4.0 inches (10.2 cm). Each of the columns 151, 152 of apertures150 includes 12 apertures, for total of 24 apertures 150 extendingthrough the cylinder 140. Each aperture 150 is 0.375 inches (0.95 cm) indiameter and is threaded. The apertures 150 are positioned such that thecenter of the first aperture 150 of the first column 151 is 1.3125inches (3.33 cm) from the first end 145 of the cylinder 140, and thefirst aperture 150 of the second column 152 is 0.9375 inches (2.38 cm)from the first end 145 of the cylinder 140. The remaining apertures 150are spaced 0.975 inches (2.48 cm) on center. The outlet port 124comprises a threaded 0.5 inch (1.27 cm) opening. Vulcan 250 wattcartridge heaters are suitable heating elements 148. In one embodiment,12 volts DC is used to power the heating elements 148.

[0056]FIG. 6 and FIG. 7 illustrate embodiments of first and second endplates 144, 160, respectively, adapted for use with the cylinder 140illustrated in FIG. 5. Referring to FIG. 6, the first end plate 144defines an opening 162 therethrough to accommodate the inlet port 122.The first end plate 144 further defines four bolt holes 164 extendingtherethrough about the periphery of the first end plate 144, with fourgenerally cylindrical spacers 166 associated with each of the bolt holes164. Four coupling feet 170 corresponding to the bolt holes 164 areconnected to the cylinder 140 (shown in FIG. 4). Four bolts 168 extendthrough the bolt holes 164, the spacers 166, and the coupling feet 170,and washers and nuts (not shown) are placed about the bolts 168 to affixthe first end plate 144 to the cylinder 140 in a sealing relationship.

[0057] In one embodiment, the first end plate 144 is 0.375 inches (0.952cm) thick with a diameter of 6 inches (15.24 cm). The inlet port opening162 comprises a threaded 0.125 inch (0.318 cm) opening, and the boltholes 164 each comprise threaded 0.250 inch (0.635 cm) openings. Thespacers 166 are each 1.250 inches (3.175 cm) long, and the bolts 168 areeach 2.50 inches (6.35 cm) long with 0.25 inch (0.635 cm) washers andnuts. The first end plate 144 further defines a sealing lip 172, whichin one embodiment, is 3.997 inches (10.152 cm) in diameter and extends0.125 inches (0.318 cm) above the surface of the first end plate 144.

[0058] Turning now to FIG. 7, the second end plate 160 includes boltholes 164, spacers 166 and bolts 168 to connect the second end plate 160to the cylinder 140 via the coupling feet 170 in a manner similar to thefirst end plate 144 as disclosed in conjunction with FIG. 6. In aparticular embodiment, the second end plate 160 further defines openingsthrough which a K-type thermocouple 180, a pressure sensor 182, and twohigh temperature thermal switches 184 extend. Suitable devices include amodel K thermocouple, a Hobbs 76062 NC pressure sensor, and VulcanCal-stat 1c1c5 high temperature thermal switches. These componentsfunction as part of a feedback system to maintain a preset pressure andtemperature in the thermal reactor 120. One high temperature thermalswitch 184 is used for over-temperature protection of the thermalreactor, while the other switch 184 is used for starter interrupt untilthe thermal reactor 120 has reached its operating temperature.

[0059] In some implementations of the fuel management system 100, theheating elements 148 are operated such that the temperature of thespecific heating elements 148 varies to achieve the desired conversionof the liquid fuel to a fuel vapor. Varying the temperature of theheating elements 148 by approximately 200° F. (93° C.) from one end ofthe thermal reactor 120 to the other creates a vortex that spreads theliquid fuel across inside surface of the cylinder, providing maximumsurface area for heating the liquid fuel to convert it to a fuel vapor.In a particular embodiment, the thermal reactor 120 includes a brass (orother heat-conducting material) matrix within the cylinder 140 that isheated by the heating elements 148. The vortex created by varying thetemperature of the heating elements 148 causes the liquid fuel to spreadabout the brass matrix to increase the surface area for heating theliquid fuel. The brass matrix also helps insure that liquid fuel ismaintained in the thermal reactor 120 until it is completely vaporized.

[0060]FIG. 8 illustrates an alternate configuration for heating theliquid fuel 112 to transform it to fuel vapor in accordance with anotherembodiment of the present invention. At least one fuel bar 190 isconnected to the side wall 146 of the cylinder 140. Two fuel bars 190are used in the particular embodiment illustrated in FIG. 8. Each fuelbar 190 defines at least one fuel well (not shown) therein. The sidewall 146 of the cylinder 140 defines a plurality of openings thatcorrespond to openings in each fuel well, such that, when the fuel bars190 are coupled to the cylinder 140 as shown in FIG. 8, the fuel wellsare in fluid communication with the cylinder 140. Each fuel well definesan inlet port 122 that is adapted to be connected to the fuel sourcesuch that the liquid fuel 112 flows into the fuel well. In oneembodiment, each fuel well includes a fuel fitting situated toperpendicularly intersect the fuel well. Each fuel well has a heatingelement 148 associated therewith disposed within the fuel bar 190, so asto heat the liquid fuel 112 within the fuel well to convert the liquidfuel 112 to the fuel vapor. The fuel vapor then enters the cylinder 140and flows out of the cylinder 140 through the outlet port 124.

[0061] In one embodiment, each fuel bar 190 is 16 inches (40.64 cm)long, 4 inches (10.16 cm) high, and 1 inch (2.54 cm) wide. Each fuel bar190 defines 24 fuel wells, which each comprise a bore 192 extendingthrough the fuel bar 190. One end of each bore 192 cooperates with acorresponding opening in the side wall 146 of the cylinder 140, and theother end of the bore 192 has a heating cartridge (not shown) insertedtherein. Suitable heating cartridges include Bosch 80025, which areheated to a temperature of about 1,450° F. to 1,472° F. (788° C. to 800°C.). In a particular embodiment, the fuel wells are lined with brassinserts to improve the conduction of heat through the bores 192. Thefluid inlet ports 122 each comprise a 0.3125 inch (0.7938 cm) hole 194extending 0.900 inch (2.286 cm) into the side of the fuel bar 190generally perpendicular to the bores 192 for the fuel wells. Each of theholes 194 for the inlet ports 122 may be provided with a filter tofilter the liquid fuel 112 entering the fuel bar 190.

[0062] The thermal reactor 120 of the fuel management system of thepresent invention addresses problems associated with known internalcombustion engines using liquid hydrocarbon fuels. The thermal reactor120 allows a complete phase change from liquid gasoline to a gaseousstate without the associated restriction of volume. All heavy ends ofthe liquid fuel are vaporized so it does not drip. The thermal reactor120 converts the liquid fuel to a vapor which puts enough random kineticenergy into the fuel so critical temperature can be reached in thecylinder and the heat of condensation does not return the fuel to aliquid state.

[0063] In the particular fuel management system 101 illustrated in FIG.2, the hot fuel vapor exits the outlet 124 of the thermal reactor 120and enters the fuel metering device 130. In one embodiment, the fuelvapor exits the thermal reactor at about 650° F. (343° C.). The purposeof the fuel metering device 130 is to operate the engine 110 as fuellean as possible for the engine's particular load condition. To thisend, a fuel metering device 130 in accordance with one embodiment of theinvention is operable between first and second stages in response to thepressure sensing device 128 to regulate the air to fuel vapor ratiobased on the load condition of the engine 110. The first stage providesfuel vapor from the thermal reactor 120 to the plenum 126 at a firstrate to achieve a first predetermined air to fuel vapor ratio, and thesecond stage provides fuel vapor from the thermal reactor 120 to theplenum 126 at a second rate to achieve a second predetermined air tofuel vapor ratio.

[0064] In a specific embodiment, the first stage is maximum lean, andthe second stage increases the fuel to air vapor ratio for acceleration.Once the acceleration requirement is met, the second stage of the fuelmetering device 130 returns the fuel vapor flow to the best leanrequirement for the engine load. In other words, the first stage iseconomy cruise, and the second stage is for power.

[0065] An exemplary fuel metering device 130 is illustrated in FIG. 9,FIG. 10 and FIG. 11. The fuel metering device 130 is operated by tworotary vacuum motors 210, 211. In other embodiments, other drivemechanisms are used, such as positive pressure. FIG. 12 is a blockdiagram illustrating a fuel management system 103 in accordance with analternative embodiment of the invention, further including an intake airventuri 220 coupled to the intake manifold 114 to provide a vacuumsource for operating the vacuum motors 210, 211. A controller 222receives an output signal from the pressure sensing device 128 and inresponse thereto, switches the fuel metering device 130 between thefirst and second stages. In the embodiment illustrated, the controller222 provides a vacuum signal from the venturi 220 to drive the vacuummotors 210, 211.

[0066] In one embodiment, the controller 222 comprises a programmablelogic array, such as a model Bimbo 1224DC010DC, which is programmedusing ROM MAX 4G software. The controller 222 operates the fuel meteringdevice 130 in response to engine load conditions as determined by thepressure sensing device 128, which may comprise a Sierra model 600 airflow meter. Other system parameters used for controlling the fuelmetering device 130 may include, but are not limited to, mass air flow,throttle position, engine speed, and liquid fuel temperature.

[0067] Referring to FIG. 11, each of the vacuum motors 210, 211 includesa cylinder 230 and a drive shaft 232 having rack gear 234 thereon. Inone embodiment, the rack gear 234 include 32 teeth per inch (12.6 teethper cm). The rack gear 234 cooperates with drive gears 236 extendingfrom a metering block 238. Each drive gear 236 is coupled to arespective rotary valve (not shown) disposed within the fuel meteringdevice 130. The fuel metering device 130 further includes a fuel vaporinlet 240 and a fuel vapor outlet 242.

[0068] In the fuel management system 103 illustrated in FIG. 12, liquidfuel enters the thermal reactor 120 and is completely converted to afuel vapor, which exits the thermal reactor 120 and enters the fuelmetering device 130. The controller compares the pressure within theintake manifold 114 as determined by the pressure sensor 128 and thevacuum signal from the intake air venturi 220, and sends a vacuum signalto the vacuum motors 210, 211 to operate the fuel metering device 130 soas to provide the leanest possible air to fuel vapor ratio for theengine's 112 load requirement.

[0069] More specifically, the fuel metering device 130 utilizes twostages. The first stage of the fuel metering device 130 is used foreconomy cruise. In this mode, the engine 110 will not produce maximumhorsepower because more air and less fuel is being introduced thusproviding a very lean air/fuel mixure. The second stage increases theair/fuel vapor ratio up to stoichiometeric thus providing the maximumair/fuel ratio for acceleration and power. In the vacuum system, twovacuum actuated Barksdale model d1h-h18ss switches are used to measureintake manifold 114 vacuum (engine load) and venturi 220 vacuum (engineRPM). When the throttle position changes, a vacuum differential switch,such as a Barksdale Vacuum Differential Switch model 0-30 hg, senses thecorresponding change in intake manifold vacuum. This switch then sends acorresponding vacuum signal to the vacuum motor associated with thefirst stage, for example, the vacuum motor 210, if the vehicle iscruising, or to the vacuum motor 211 associated with the second stage ifthe vehicle is accelerating.

[0070] Turning now to FIG. 13, an exemplary embodiment of the plenum 126is illustrated. The plenum provides more time for the air and fuel vaporto mix for enhanced combustion. It also provides additional mass todampen the reflecting waves that bounce off of the engine's intakevalves when they close, thereby preventing intake air from backing outof the engines intake manifold 114. The plenum 130 illustrated in FIG.13 includes a generally cylindrical central portion 250, an inlet end252 through which the air and fuel vapor is received, and an outlet end252, which is adapted to be connected to the intake manifold 114. Thecentral portion 250 may suitably be fabricated out of brass 360,stainless steel 420, or a ceramic material. In a particular embodiment,glass is used for the central portion 250 to allow visual observation ofthe air and fuel vapor mixture flowing through the plenum. In oneembodiment, the cylindrical central portion 250 is about 10 inches (25.4cm) long with a diameter of 4 inches (10.16 cm), though these dimensionswill vary dependent on the engine's intake velocity range.

[0071] The particular fuel management system of the present inventionthat is illustrated in FIG. 12 includes an intake air velocity controlvalve 260 coupled between the fuel metering device 130 and the plenum126. Referring to the plenum illustrated in FIG. 13, the intake airvelocity control valve 260 is coupled to the inlet end 252 of the plenum126. The intake air velocity control valve 260 is operated, for example,by a vacuum motor 261, and includes an air inlet 262 at a first end, anda second end 264 that is coupled to the inlet end 252 of the plenum. Theintake air velocity control valve 260 defines an air flow path (notshown) between the air inlet 262 and the second end 264, and a variableair flow restrictor (not shown) positioned within the air flow path. Inone embodiment, a butterfly valve is used, and in another embodiment, arotary valve is used.

[0072] In the fuel management system 103 illustrated in FIG. 12, the hotfuel vapor leaves the fuel metering device 130 and flows through theintake air velocity control valve 260. The intake air velocity controlvalve 260 increases the engine's volumetric efficiency at low speeds byincreasing the speed of the air and fuel vapor mixture, allowing moreair to enter the engine's 110 combustion chamber while the intake valveis open. Further, a vane in the throat of the intake air velocitycontrol valve 260 causes the intake air to swirl, resulting in a vortexthat thoroughly mixes the air and fuel vapor molecules as they enter theplenum 126. The intake air velocity control valve 260 is operated tomaintain a predetermined vacuum (for example, 10 in/h20 vacuum) on theplenum 126. As discussed above, the plenum 126 provides additional timefor the air and fuel vapor to mix, allowing the mixture to completelycombust.

[0073] From the engine's intake manifold 114, the air and fuel vapormixture enters the engine's 110 combustion chamber where it burns andexits the exhaust system at high velocity, common with all internalcombustion engines. The high exhaust velocity creates a vacuum in theexhaust pipes, which is used to pull fresh air into the engine'scylinders during the camshaft overlap period of the intake stroke. Thisimproves volumetric efficiency and maximum engine torque. This pulsescavenging of the cylinders is typically tuned for the engine's RPMassociated with maximum torque. However, at any engine speed belowmaximum torque, the engine is over scavenged, resulting in a lowertorque curve at lower engine speeds. This is an engineering compromiseassociated with known internal combustion engines.

[0074]FIG. 14 illustrates an exhaust control system 300 in accordancewith an embodiment of the fuel management system of the presentinvention. The exhaust control system 300 prevents or reduces cylinderover scavenging during the overlap period of the camshaft in theinternal combustion engine 110. The exhaust gas flows from an exhaustmanifold 310, through an exhaust pipe 312 to a muffler 312. An exhaustvelocity control valve 320 is connected between the exhaust manifold 310and the muffler 312 to restrict the exhaust gas velocity just to thepoint that nominal back pressure prevents fresh air from entering theexhaust manifold 310—typically at low speed. In one embodiment, a rotaryvalve is used for the exhaust velocity control valve 320. A vacuum motor322, for example, may be used to operate the exhaust velocity controlvalve 320 in response to a pressure sensor 324 that is adapted todetermine the exhaust gas back pressure. In the illustrated embodiment,the pressure sensor 324 is coupled to the exhaust manifold. The vacuummotor 322 may operate the exhaust velocity control valve 320 in responseto additional, or other, desired engine parameters, such as engine load(as determined by the pressure sensor 128) and RPM requirements.

[0075] In another specific embodiment of the fuel management system, anexhaust system thermal reactor 340 is coupled to the exhaust manifold310 so as to use spent exhaust gas energy for partial heating of theliquid hydrocarbon fuel. In a system employing the exhaust systemthermal reactor 340, the exhaust velocity control valve 320 furtherfunctions to insure that the exhaust system thermal reactor 340 isfilled with exhaust gases throughout the range of engine conditions. Theexhaust system thermal reactor 340, however, only provides heating ofthe liquid fuel 112 when the engine 110 is at operating temperature.Thus, the exhaust system thermal reactor 340 is used for partial heatingof the liquid fuel; the thermal reactor 120 controls the final fuelvapor outlet temperature and provides cold start capability.

[0076]FIG. 15 illustrates an exemplary embodiment of an exhaust systemthermal reactor 340. The exhaust system thermal reactor 340 comprises around cylinder 342 that is packed with a conductive matrix (not shown).The exhaust pipe 312 passes through the center of the cylinder 342 toheat the matrix. A fuel dispersion tube 344 is positioned above theexhaust pipe 312 to spray liquid fuel through the matrix and over theexhaust pipe 312. The fuel dispersion tube 344 defines a plurality ofholes for distributing the liquid fuel. In a particular embodiment, thefuel dispersion tube defines 56 holes, each having a diameter of 0.015inch (0.381 mm). The holes are arranged with an included angle of 90°drilled longitudinally on the tube to distribute the liquid fuel evenlyover the exhaust pipe 312 and through the matrix, thus providing themaximum surface area for heating the fuel.

[0077] Some internal combustion engines, such as a gasoline engine, usea spark ignition system. Diesel engines use an auto-ignition system.When the fuel management system, and particularly the thermal reactor ofthe present invention, is used in conjunction with a diesel engine,auto-ignition of the air and fuel vapor mixture is no longer possible.Therefore, another form of ignition is necessary. In accordance withaspects of the invention, a combustion chamber glow plug system isprovided. The glow plug system is illustrated in FIG. 16 The glow plugsystem 370 includes a plurality of adapters 372 for replacing dieselfuel injector nozzles with diesel engine glow plugs 374, such as Delco11G glow plugs, such that at least a portion of the glug (i.e., the glowplug tip) extends into the engine's combustion chamber or pre-combustionchamber. This provides a source of fuel mixture ignition, instead of theauto-ignition method typically used with diesel engines.

[0078] In one embodiment of the glow plug system 370, the tiptemperature of the glow plugs 372 is varied from 1,200° F. to 1,550° F.(649° C. to 843° C.). A control module 376 controls the tip temperaturein response to predetermined engine parameters, such as engine load andRPM, thus providing a mechanism for advancing or retarding the engine'signition timing based on the desired engine parameter. An example of asuitable control module 376 is a Red Lion PAXT0000 that includes anECG2764 EPROM. The system is responsive to the intake manifold pressuresensor 128 (engine load) and a tach sensor (engine RPM). When the engineload increases, manifold vacuum decreases which lowers the temperatureof the glow plugs 372. At idle speed, the temperature of the glow plugs372 is about 1,550° F. (843° C.), and the temperature decreases to about1,200° F. (649° C.) under full load. When the engine RPM exceeds maximumtorque, the control module 376 is programmed to increase the glow plug372 temperature to compensate for the engine's loss in volumetricefficiency. In a specific embodiment, the temperature of the glow plugs372 is increased by the same percent as the volumetric efficiency loss.

[0079] In accordance with another aspect of the present invention, anovel process for dynamically mapping operating parameters of the engine112 is provided. Calibrating or otherwise adjusting the multiplecomponents of an engine system, such as the fuel management system ofthe present invention, requires simultaneously studying and analyzing amyriad of engine operating parameters. To further complicate theanalysis, the engine parameters are constantly changing depending on theengine load, speed, etc.

[0080]FIG. 17 is a flow diagram illustrating a mapping process inaccordance with the present invention. In block 400, a plurality ofmeasurement devices are configured to indicate a plurality of engineparameters to be analyzed. In block 402, the engine is operated asdesired. The outputs of the measurement devices are then recorded whilethe engine is operating in block 404. After the engine has been operatedfor the desired time, and/or through the desired operational criteria,the recorded outputs are played back at predetermined time intervals inblock 406. This allows the technician to view the recorded parameters atany given time as desired to analyze various parameters occurringsimultaneously, even if a given parameter occurs for only a short timeperiod. For example, the outputs of the measurement devices may berecorded on a digital recording device, such as a personal computer harddisk, or the outputs may be video taped.

[0081] A Panasonic Pro 456AG video camera is a suitable video taperecorder. In specific implementations, the recorded parameters includefuel vapor pressure, intake manifold pressure, temperature, relativehumidity, altitude, engine oil temperature, battery voltage, liquid fuelpressure, engine coolant temperature, etc. Further, a performancecomputer, such as a Veri-Com VC2000 performance computer, may be used tomeasure and display other parameters in real time, which may then berecorded for subsequent play back in accordance with the method of thepresent invention. Such parameters include G-force, time, speed,distance, horsepower, RPM, torque and gear ratio. Further, theseparameters are measured at 0.01 second intervals.

[0082] Thus, the present invention provides a system that may be used inconjunction with conventional internal combustion engines using liquidhydrocarbon fuels, such as gasoline, diesel, methanol, ethanol, etc. Thefuel management system permits complete combustion of the air and fuelvapor mixture, thereby significantly reducing exhaust emission levelsand improving fuel economy. Moreover, the system disclosed hereinfunctions to reduce cold start emissions to levels comparable to naturalgas or propane fueled vehicles.

[0083] It will be appreciated by those of ordinary skill in the arthaving the benefit of this disclosure that the embodiment illustratedabove is capable of numerous variations without departing from the scopeand spirit of the invention. It is fully intended that the invention forwhich a patent is sought encompasses within its scope all suchvariations without being limited to the specific embodiment disclosedabove. Accordingly, the exclusive rights sought to be patented are asdescribed in the claims below.

What is claimed is:
 1. A thermal reactor for converting a liquidhydrocarbon fuel to a fuel vapor, comprising: a cylinder defining anaxial bore therethrough, the cylinder defining an inlet port adapted toreceive the liquid hydrocarbon fuel, the cylinder defining an outletport adapted to discharge the fuel vapor; and at least one heatingelement connected to the cylinder and arranged to heat the liquidhydrocarbon fuel to convert the liquid fuel to the fuel vapor.
 2. Thethermal reactor of claim 1, wherein the at least one heating elementcomprises a plurality of heating elements disposed in the cylinder, theheating elements arranged such that the liquid hydrocarbon fuel contactsthe heating elements.
 3. The thermal reactor of claim 2, wherein thecylinder defines a side wall having a plurality of aperturestherethrough, each of the apertures having one of the heating elementsextending therethrough such that each heating element projects into thecylinder.
 4. The thermal reactor of claim 3, wherein each of the heatingelements is generally perpendicular to the axis of the cylinder.
 5. Thethermal reactor of claim 3, wherein each of the apertures has acorresponding aperture located about 90 degrees therefrom.
 6. Thethermal reactor of claim 3, wherein the apertures are arranged in twocolumns, each column being generally parallel to the axis of thecylinder, the columns being positioned about 90 degrees apart.
 7. Thethermal reactor of claim 1, further comprising: at least one fuel barconnected to a side wall of the cylinder, the fuel bar defining at leastone fuel well in fluid communication with the cylinder, the fuel welldefining the inlet port such that the liquid fuel flows into the fuelwell; wherein the at least one heating element is disposed within thefuel bar so as to heat the liquid fuel within the fuel well to convertthe liquid fuel to the fuel vapor.